Journal of Physical Chemistry A, Vol.106, No.25, 6206-6212, 2002
Photoejection of electrons from cycloocta[1,2,3,4-def;5,6,7,8-d'e'f]bisbiphenylene radical-anion and dianion derivatives: Identification of a light-induced disproportionation
Photoejection of electrons from 2,5,8,11-tetra-tert-butylcycloocta[1,2,3,4-def;5,6,7,8-d'e'f']bisbiphenylene radical anion, BPD.-, and the respective dianion, BPD2-, are described. Photoejection of an electron from BPD2- yields a [BPD.-...e(-)] cage complex and separated BPD.- and e(-)/Li+ species. Recombination of the cage photoproducts proceeds at room temperature with a rate constant of k(rec)(1) = (7.0 +/-0.2) x 10(5) s(-1), and the separated photoproducts recombine by a diffusional back-electron-transfer rate constant of k(rec)(2) = (1.5 +/- 0.2) x 10(9). M-1.s(-1). Photoejection of the electron from BPD.- yields the neutral pi-system, BPD, and the ejected electron reduces an unreacted BPD.- to form BPD2-. The photoejection of the electron from BPD.- thus yields the disproportionation products, BPD and BPD2-. The disproportionation products recombine by a diffusional process, k(rec) = (1.0 +/- 0.2) x 10(10) M-1.s(-1) (at room temperature).